The present invention relates generally to scroll compressors and more specifically to capacity modulation systems of the delayed suction type for such compressors.
A wide variety of systems have been developed in order to accomplish capacity modulation most of which delay the initial sealing point of the moving fluid pockets defined by the scroll members. In one form, such systems commonly employ a pair of vent passages communicating between suction pressure and the outermost pair of moving fluid pockets. Typically these passages open into the moving fluid pockets at a position normally within 360.degree. of the sealing point of the outer ends of the wraps. Some systems employ a separate valve member for each such vent passage which valves are intended to be operated simultaneously so as to ensure a pressure balance between the two fluid pockets. Other systems employ additional passages to place the two vent passages in fluid communication thereby enabling use of a single valve to control capacity modulation.
More recently a capacity modulation system for scroll compressors of the delayed suction type has been developed in which a valving ring is movably supported on the non-orbiting scroll member. An actuating piston is provided which operates to rotate the valving ring relative to the non-orbiting scroll member to thereby selectively open and close one or more vent passages which communicate with selective ones of the moving fluid pockets to thereby vent the pockets to suction. A scroll-type compressor incorporating this type of capacity modulation system is disclosed in U.S. Pat. No. 5,678,985 the disclosure of which is hereby incorporated by reference. In this capacity modulation system, the actuating piston is operated by fluid pressure controlled by a solenoid valve. In one version of this design, the solenoid valve and fluid pressure supply and vent lines are positioned externally of the compressor shell. While such an arrangement offers the advantages of ease of assembly as well as replaceability of the solenoid valve to accommodate different system operating voltages, the external piping is exposed and hence subject to potential damage during assembly/handling, shipment and/or installation.
In another version, the solenoid valve and actuating fluid supply lines are all located internally of the hermetic shell thus avoiding the potential for damage to the fluid supply lines. However, because the solenoid valve is not accessible once the hermetic shell is welded, varied available operating voltages for the solenoid can not be easily accommodated nor can the actuating coil of the solenoid valve be easily replaced in the event of failure thereof.
The present invention overcomes these disadvantages by providing a capacity modulation system utilizing the actuating ring approach in which all of the fluid supply lines and associated control valving are located within the hermetic shell but the actuating coil of the solenoid valve is mounted on the outer surface of the hermetic shell. Thus the fluid supply lines are protected from damage during shipment and installation of the compressor while the external mounting of the actuating coil enables the system to be easily adapted to most any available operating voltage. Further, the actuating coil may be easily replaced in the event of malfunction. Additionally, this system facilitates production lines testing of the capacity control modulation system prior to final welding of the hermetic shell via an appropriately designed fixturing system.
Additional advantages and features of the present invention will become apparent from the subsequent description and the appended claims taken in conjunction with the accompanying drawings.